Gate-tuned high frequency response of carbon nanotube Josephson junctions

TL;DR

This paper investigates how the high-frequency response of carbon nanotube Josephson junctions can be tuned using a gate voltage, revealing gate-dependent phase dynamics and capacitance effects.

Contribution

It demonstrates gate-controlled superconducting switching and phase damping in CNT Josephson junctions, modeled by an RCSJ framework with a gate-dependent capacitance.

Findings

Gate voltage modulates the switching current.

Phase dynamics damping depends on gate voltage.

Effective capacitance varies strongly with gate.

Abstract

Carbon nanotube (CNT) Josephson junctions in the open quantum dot limit exhibit superconducting switching currents which can be controlled with a gate electrode. Shapiro voltage steps can be observed under radiofrequency current excitations, with a damping of the phase dynamics that strongly depends on the gate voltage. These measurements are described by a standard RCSJ model showing that the switching currents from the superconducting to the normal state are close to the critical current of the junction. The effective dynamical capacitance of the nanotube junction is found to be strongly gate-dependent, suggesting a diffusive contact of the nanotube.